Viacom’s rapidly-expanding MTVi online division has taken on 144,000 more square feet of space at its downtown Internet headquarters.

The entertainment giant signed for the space on the ninth and 10th floors in the massive building at 770 Broadway, which takes up an entire square block.

The deal was brokered by Michael Laginestra and Scott Gottlieb of Insignia/ESG. Both declined comment.

The MTVi group, a unit of MTV Network, includes MTV.com, rated as the No. 1 music content site on the Web; VH1.com, a site geared towards the 25-plus age category, and SonicNet.com, a site offering music and information on a wide range of topics.

They will also house VNU, the Netherlands-based company that publishes Adweek, Billboard magazine and New York offices of The Hollywood Reporter.

Last Summer, VNU leased a major 465,000- square-foot chunk of space — considered the largest transaction of the year.

The magazines are relocating from 1515 Broadway, where MTV’s Times Square studio is located. They are expected to move into their new digs in March.

In the two floors above MTVi are the executive offices of J. Crew.

In 1998, CBS — which is to be acquired by Viacom — was reportedly in talks with the landlord to move its studios there before signing with the General Motors building.